In the human vertebral column and especially in the lumbar vertebral column, the intervertebral disk (spinal disk) connects an upper osseous vertebral body in an articulated manner with a lower osseous vertebral body.
Such an artificial intervertebral disk is known, for example, from European patent application EP 0 610 837 B1 in which two plates are joined to each other by an elastomer core. The elastomer core has an upper part and a lower part that enclose an intermediate part whose peripheral surface is concave. In this manner, when bending moments or transmission forces are exerted onto the intervertebral disk, the forces generated on the contact surface between the plates and the core should be reduced in comparison to a core having straight sides.
U.S. Pat. No. 3,867,728 describes an intervertebral disk that consists, for example, of one single piece and that has a concave outer surface.
Moreover, U.S. Pat. No. 5,071,437 describes a spinal disk prosthesis comprising an upper flat plate, a lower flat plate, and a flat elastomeric core interposed between said plates.
EP 0 747 025 B 1 describes an artificial spinal disk for use between adjacent vertebrae, with a first component having a concave recess as well as a second component having a projection that fits into the recess of the first component so that an unrestricted tilt-and-turn movement is achieved between the first component and the second component.
Furthermore, DE 100 24 922 C1, EP 10 41 945 A1, WO 02/080818 A1, U.S. Pat. No. 6,368,350, DE 42 13 771 C1, EP 05 60 140 B1, EP 13 44 508 A1, EP 13 44 507 A1, DE 42 08 115 A1, EP 12 87 795 A1, DE 102 42 329 A1 and DE 197 10 392 C1 also disclose other spinal disk prostheses.
A drawback of all of the artificial intervertebral disks known so far is that the natural joint properties can only be insufficiently replicated. The patient clearly perceives this restriction of the natural range of motion as causing discomfort when several vertebral bodies have been replaced, as a result of which the disadvantageous properties of the intervertebral disks multiply.